An image forming apparatus has a clock supply circuit supplying a signal at a first clock frequency or a second clock frequency lower than the first frequency, a first CPU performing image data processing based on the signal, and a second CPU measuring time based on the signal to determine execution timing of each process performed in control processing. The image forming apparatus includes a load determination unit determining whether a load of the image data processing is higher than a reference level, and a control unit that switches the frequency to the first frequency when the load is higher than the reference level, and to the second frequency when the load is not higher. When the frequency switching occurs, the second CPU changes a method for measuring time. The second CPU completes one process before the switching and starts the next one after the switching.
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1. An image forming apparatus having a system on a chip (SoC) on which, a clock supply circuit, a first CPU, and a second CPU are integrated, the clock supply circuit supplying a clock signal while switching a frequency of the clock signal between a first clock frequency and a second clock frequency that is lower than the first clock frequency, the first CPU performing image data processing in synchronization with the clock signal supplied by the clock supply circuit, and the second CPU measuring time with reference to the clock signal supplied by the clock supply circuit and determining, based on the measured time, execution timing of each of a series of processes performed in control processing other than the image data processing, the image forming apparatus comprising: a load determination unit that determines whether image data to be processed by the first CPU meets a predetermined criteria; and a control unit that controls the clock supply circuit to switch the frequency of the clock signal to the first clock frequency when the load determination unit determines that the image data to be processed by the first CPU meets the predetermined criteria, and to switch the frequency of the clock signal to the second clock frequency when the load determination unit determines that the image data to be processed by the first CPU does not meet the predetermined criteria, wherein when the clock supply circuit performs the switching between the first frequency and the second frequency, the second CPU switches a method for measuring time between a first method corresponding to the first clock frequency and a second method corresponding to the second clock frequency, thereby avoiding variation in the execution timing, and the second CPU completes one process among the series of processes before the switching of the frequency and starts the next one of the series of processes after the switching of the frequency.
An image forming apparatus (like a printer or copier) contains a single chip (SoC) integrating a clock circuit, a first CPU, and a second CPU. The clock circuit switches the clock signal frequency between a faster (first) and slower (second) frequency. The first CPU processes image data in sync with this clock. The second CPU tracks time using the clock signal to schedule control tasks separate from image processing. A load determination unit assesses if the image data processing load meets certain criteria. A control unit then switches the clock to the faster frequency if the load is high, and the slower frequency if it's low. When switching frequencies, the second CPU changes its method of timing to maintain consistent task execution, completing one task before the switch and starting the next after the switch.
2. The image forming apparatus according to claim 1 , wherein the series of processes include a series of sheet transport processes for transporting a recording sheet used for image formation along a transport path to a sheet ejection position, one or more positions are predetermined along the transport path, and the series of sheet transport processes include a process for transporting the recording sheet to, and holding the recording sheet at one of the one or more predetermined positions.
The image forming apparatus described previously, where the clock frequency is adjusted based on processing load, involves a series of processes for moving paper along a path to the output. The processes specifically include moving and pausing the paper at defined positions along this path. These defined positions are predetermined locations within the paper transport system. The process ensures paper arrives at the correct place and time during printing.
3. The image forming apparatus according to claim 2 , wherein the one or more predetermined positions include a position at which the leading edge of the recording sheet comes into contact with a nip formed between a pair of timing rollers that determine timing for transporting the recording sheet to an image transfer position.
The image forming apparatus that adjusts clock speed based on processing load, and includes paper transport processes with pauses at predetermined positions, has at least one of these positions being the point where the paper's leading edge touches the "nip" (contact point) of timing rollers. These timing rollers control when the paper moves to the image transfer area, ensuring precise timing for image application.
4. The image forming apparatus according to claim 2 , further comprising: a sheet housing unit that houses recording sheets used for image formation, wherein the sheet transport processes include a process for feeding the recording sheets from the sheet housing unit to the transport path one by one, and the second CPU suspends feeding of a recording sheet before the switching and resumes the feeding after the switching.
The image forming apparatus which adjusts clock frequency based on processing load and manages paper transport processes with pauses at predetermined positions, includes a paper tray. The paper transport process further includes feeding paper one sheet at a time from this tray onto the transport path. The second CPU controls this feeding. Before switching clock frequencies, the paper feeding is paused. After the switch, feeding resumes, preventing timing errors caused by the clock frequency change.
5. The image forming apparatus according to claim 1 , further comprising: an image forming unit that forms a toner image; and an intermediate transfer belt to which the toner image formed by the image forming unit is primarily transferred and which transports the primarily transferred toner image to a position where the primarily transferred toner image is secondarily transferred to the recording sheet, wherein the series of processes include an image stabilization process performed by primarily transferring toner patches on predetermined positions on the intermediate transfer belt.
The image forming apparatus described earlier, which adjusts the clock frequency based on processing load, also features an image forming unit that creates toner images and an intermediate transfer belt. The toner image is first transferred to this belt and then to the paper. The series of processes managed by the second CPU includes an image stabilization process. This involves transferring toner patches to specific locations on the intermediate transfer belt, ensuring image quality and consistency.
6. The image forming apparatus according to claim 1 , wherein the series of processes include a cleaning process for cleaning residual toner after completion of image formation.
In the described image forming apparatus, which adjusts clock frequency based on processing load, the processes include a cleaning process. This cleaning process removes any remaining toner after printing is complete.
7. The image forming apparatus according to claim 1 , further comprising: a switch prohibiting unit that prohibits the clock supply circuit from switching the frequency until a predetermined period elapses after the previous switching of the frequency.
The previously described image forming apparatus, which adjusts the clock frequency based on processing load, also has a switch prohibition unit. This unit prevents the clock frequency from switching too frequently. It enforces a minimum time period that must pass after a previous frequency switch before another switch can occur, adding stability to the system.
8. The image forming apparatus according to claim 1 , wherein the load determination unit stores therein a first reference value and a second reference value indicating a higher processing load than a processing load indicated by the first reference value, and the load determination unit refers to the first reference value as the predetermined criteria when the current frequency is the first clock frequency, and refers to the second reference value as the predetermined criteria when the current frequency is the second clock frequency.
The image forming apparatus that adjusts clock frequency depending on processing load, uses a load determination unit that stores two reference values: a first and a second. The second value represents a higher processing load than the first. When the clock is already running at the faster (first) frequency, the load determination unit uses the *first* reference value to decide if a switch to the slower frequency is needed. Conversely, when the clock is running at the slower (second) frequency, it uses the *second* reference value to decide if a switch to the faster frequency is needed. This hysteresis prevents rapid, unnecessary switching.
9. The image forming apparatus according to claim 1 , wherein the first CPU starts the image data processing after the switching of the frequency.
In the image forming apparatus, which adjusts the clock frequency based on processing load, the first CPU only starts processing image data *after* the clock frequency has been switched to the appropriate speed based on the current processing load. This ensures that the image processing occurs at the correct clock speed for optimal performance.
10. The image forming apparatus according to claim 1 , wherein the predetermined criteria is met when the image data to be processed by the first CPU includes objects other than characters.
In the described image forming apparatus which adjusts clock speed based on processing load, the system determines that the image data processing load is "high" (and therefore needs a faster clock speed) if the image data includes objects other than characters. The presence of non-character objects, like images or graphics, triggers the switch to the higher clock frequency.
11. The image forming apparatus according to claim 1 , wherein when the current frequency is the first clock frequency the load determination unit determines that the predetermined criteria is met when the image data to be processed by the first CPU includes color image processing, when the current frequency is the second clock frequency the load determination unit determines that the predetermined criteria is met when the image data to be processed by the first CPU includes monochrome image processing.
In the described image forming apparatus that adjusts clock frequency according to processing needs, the criteria for needing the faster clock depends on the *current* clock frequency. If the clock is currently at the faster speed, the system decides image processing requires the higher clock speed when color image processing is being performed. However, if the clock is currently at the slower speed, the system decides that image processing requires the higher clock speed even when only monochrome (black and white) image processing is being done. This allows for quick processing of both color and monochrome images.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
August 19, 2014
September 12, 2017
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